Electric lamp



April 25, 1939. H. KREFFT ET AL 2,156,057

ELECTRIC LAMP Filed -April 7, 1938 Inventors; Hermann Krefft, Kurt Larche,

JO 76 41/14 6.x]

y Their Attorn ey Patented Apr. 25, 191 39 UNITED STATES PATENT- OFFICE ELECTRIC LAMP Hermann Kreflt, Berlin-Friedrichshagcn, and

Kurt Lareh, Berlin-Tempclhof. Germany, assignors to General Electric Company, a corporation of New York Application April 7, 1938, Serial No. 200,780

In Germany April 30, 1937 '1 Claims. (01. 176-16) Our invention relates to electric lamps gentype with a suitable starting device arranged erally and to a suitable starting arrangement entirely within the lamp itself. therefor. More particularly, our invention re-- Still another object of our invention is to prolates to a starting arrangementfor electric lam & vide an incandescent high-pressure vapor lamp of the high-pressure incandescent type in whlc with a starting device comprising an electrical 5 a vaporizable metal contained within the lamp is resistance in series with the lamp filament and vaporized during operation thereof. a second resistance, having a negative tempera- It has beenproposed heretofore to use as ature coefflcient, connected in parallel with said filling for electric incandescent lamps a highseries resistance and adapted to automatically pressure metal vapor, particularlymercury vapor, short circuit the said series resistance during 10 in order to thereby reduce the vaporization of operation of. the lamp. the lamp filament to an even greater extent than A further object of our invention is to prois accomplished by a rare gas filling, and in order vide an incandescent high-pressure vapor lamp to be able to heat the said filament to a higher with a starting device of the above type in which degree without detrimentally influencing its life. the series resistanceis utilized as a heating body it The higher temperature, of course, is coincidento accelerate the formation of the metallic vapor tal with a higher light yield and higher lightw h n the p, thereby reducing th tarting intensity. v time of the lamp to a considerable extent.

It is also known that such high-pressure vapor In the incandescent hig -P -D p lamps, having a filament dimensioned for a high according to our invention, the series resistance 9 current value, cannot be connected directly to and the resistance with the negative temperature the full network voltage for several reasons. coeflicient may be advantageously arran ed in In the first place, the filament carrying such a. the lamp base. In the case of double-walled high load will vaporize extremely rapidly when high-pressure vapor lamps provided with an en- 26 the metal vapor pressure in the lamp. is low, closing vessel, the above-mentioned resistances a such as exists when the lamp is cold. In addl may be placed together either within the interior tlon. the high voltage drop across the lamp filaof such enclosing vessel or in the lamp base, or ment tends to produce short circuits when the they may be arranged separate from each other vapor pressure in the lamp is not sufliciently in the two spaces.

30 high. The occurrence of such short circuits is Further object nd a v n a of Our inven- 3c objectionable inasmuch as they destroy the lamp. tion will appear from the following description Various means have been suggested for avoiding of a species thereof and from the accompanying the above-mentioned disadvantages, such as condrawing which is a-side view, Partly in on. necting a current-limiting resistance in the curof an incandescent high-P l a p rent-supply wires and then short circuiting this comprisin our invention. 35

resistance after the lamp has been heated up Referring to the drawing, thelamp there shown and the'vapor pressure therein sufllciently high; compllees an Outer 81101081118 bulb of v l p l or by first connecting'several similarly designed f 81385 ill-Which 18 m p r y at h high-pressure vapor lamps i series and later, center thereof, an incandescent lamp 2 of the after the lamps are heated up, connecting themgh'pressure metallic, V9430! type- The said 40 same in parallel to the network. In spite of the lamp 2 consists of a small tubular bulb or above suggestions mgh pressu re vapor lamps velope 2' of quartz or other hard heat-resisting have not as yet been introduced in practical apglasfi and coiled filament 3 mounted within Said plications because of necessary special switchtubular envelope and disposed along the axis of 1 8 accessories and switching procedures which same The filament 3 is supported within the tubular envelope 2' by means of current suprdilanlizthe operation of the lamp considerably more my wires 4, 5 sealed opposite ends of the tubul b 2' One ob ect of our invention is to provide g i$%g i:2{ connected to pp 6 high-pressure vapor lamp of the incandescent v I The incandescent lam lo a n a starting device arranged theresmall quantity a 'of. a $3221.12" m etif l fifi a with which s extremely Simple in c nstruction mercury, whichispreferably dimensioned in such and which operates automatically and reliably. a way that it completely vaporizes during the Another object of our invention is to.-provide damp starting period while forming the desired 5 a high-pressure vapor lamp of the incandescent vapor pressure'within the said bulb 2'. In other 5 vwords, the quantity of vaporizable metal 6 within the envelope 2' is so apportioned that during lamp operation the metallic vapor is superheated so that an unpermissible rise in the pressure of the lamp filling need not be feared even when voltage and current fluctuations occur, or when the lamp is mounted within fixtures that are closed and which dissipate the heat very slowly.

The lamp envelope 2' contains, in addition to the vaporizable metal 6, a suitable gas filling, such as, for instance, a mixture of nitrogen and argon or krypton.

A base 1, consisting of a threaded metallic shell 8, insulation 9, and a bottom end contact I II, is mounted on the neck portion of the outer bulb I, preferably by means of suitable cement II. The current supply wire 5 is directly connected to the base shell 8 by spring contact l2, lamp support l3 and lead wire II. The other current supply wire 4 is connected to the bottom end contact l0 through spring contact [5, lamp support itself form a part of the filament 3.

Mounted within the base I of the lamp is a resistance 20 which has a negative temperaturecoefficient and which is arranged to short circuit the series resistance l8, during operation of the lamp, by means of the lead I'I and a connection 2| to the lead wire IS. The resistance 20 consists preferably of low metal oxides, such as uranium dioxide or a mixture of titanium dioxide and magnesium oxide. Such resistances, in the cold state, have a relatively high electrical resistance which decreases rapidly upon heating up of the said resistance and which is negligibly small at the operating temperature. The initial heating time and the cooling time of such a resistance 20 with a negative temperature coefilcient depend on the composition of the, material comprising the said resistance, the. thermal capacity thereof and the cooling conditions, and

' can be readily adapted to the rise in the vapor pressure in the incandescent lamp 2 when the same is placed in operation. In order to avoid detrimental overloadsit is advisable to so design and arrange the resistance 20 with the negative temperature coeflicient that when the lamp is placed in operation the said resistance 20 will not heat more rapidly than the vapor filling in the incandescent lamp 2, and when the lamp is turned off the said resistance cools at least as rapidly as '2' to an increasing extent with a corresponding increase in the pressure of the metal-vapor fill The said series resistance l8 consists ing therein. At the same time, the resistance 20 is also heated by the small current flowing through the same so that its resistance will gradually drop more and more until finally, when the operating vapor pressure of the metal-vapor filling is attained, its resistance value will have become so negligibly small that it then short circuits the series resistance l8.

Since the starting device according to ourv invention does not function abruptly, like mechanical switching devices, but instead functions gradually, it provides the possibility. of selecting, at each instant during the lamp starting operation, the largest lamp heating current permissible in view of the vapor pressure existing in the lamp 2 at the particular moment.

By mounting the coiled tungsten wire I8, comprising the series resistance, closely adjacent the incandescent lamp bulb 2', it accordingly acts as a heating body to heat up the incandescent lamp bulb 2' during the lamp starting operation.

'The effect of this auxiliary heating is to accelerate the formation of the metallic vapor within the incandescent lamp 2, thereby reducing the starting time of such lamp to a considerable extent.

What we claim as new and desire to secure by Letters Patent of the United States is: u

1. In combination, an electric lamp comprising an envelope, a metallic filament sealed therein, and a quantity of vaporizable metal within an envelope, a metallic filament sealed therein,

and aquantity of vaporizable metal within said envelope, and a starting device for said lamp comprising a starting resistance connected in series with said filament, said starting resistance being formed as a heating body and mounted closely adjacent said envelope, and a second resistance, having a negative temperature coefficient, connected in parallel with said starting resistance to thereby short circuit the latter during operation of the lamp.

.3. In combination, an electric lamp compriseing an envelope, a metallic filament sealed therein and including a series resistance having a positive temperature coefficient, and a 'quantity of vaporizable metal within said envelope, and a starting device for said lamp comprising the saidseries resistance and a second resistance, having a negative temperature coeflicient, connected in parallel with said series resistance to a thereby short circuit the latter during operation of the lamp.

4.- In combination, en electric lampcomprising an envelope, a metallic filament sealed therein,

and a quantity of vaporizablemetal within said envelope, and a starting device for said lamp comprising a starting .resistance connected in series with said filament and asecond resistance, having a negative temperature coefficient and consisting of low metal oxides, connected in parallel with said starting resistance to thereby short circuit the latter during operation of the lam a 5. In combination, an electric lamp coin riscomprising a starting resistance, having a positive temperature coefllcient, connected in series with said filament and a second resistance, having a negative temperature coefiicient, conne ted in parallel with said starting resistance to the by short circuit the latter during operation of he lamp, said second resistance being so constru ted and arranged as to heat up no faster than the vapor filling in said lamp when the said lamp is placed in operation and to cool at least as rapidly as said vapor filling upon discontinuance of such lamp operation.

6. An electric lamp comprising an outer envelope, a high-pressure incandescent lamp mounted within said outer envelope, said incandescent lamp comprising a bulb containing a metallic filament and a quantity of vaporizable metal, and a starting device arranged within said electric lamp and comprising a starting resistance connected in series with said filament and a second resistance, having a negative temperature millcient, connected in parallel'with said starting resistance to thereby short circuit the latter during operation of the said high-pressure incandescent lamp.

'7. An electric lamp comprising an outer envelope, a base secured thereto, a high-pressure'incandescent lampmounted Within said outer envelope, said incandescentlamp comprising a bulb containing a metallic filament and a quantity of vapprizable metal, and a starting device arranged within, said lamp, comprising a starting resistance mounted within said outer envelope and connected in series with said filament and a second resistance, having a negative temperature coeflicient, mounted within said base and connected in parallel with said starting resistance to thereby short circuit the latter duringoperation of the lamp;

said starting device HERMANN jKURT LARCHE; 

